Update clean-css to version 5.1.1 (tailwindlabs#3778)

Co-authored-by: depfu[bot] <23717796+depfu[bot]@users.noreply.github.com>

Author: depfu[bot]

package.json

@@ -43,7 +43,7 @@
     "@babel/preset-env": "^7.13.8",
     "autoprefixer": "^10.2.5",
     "babel-jest": "^26.6.3",
-    "clean-css": "^4.1.9",
+    "clean-css": "^5.1.1",
     "eslint": "^7.22.0",
     "eslint-config-prettier": "^7.2.0",
     "eslint-plugin-prettier": "^3.3.1",

yarn.lock

@@ -2086,10 +2086,10 @@ class-utils@^0.3.5:
     isobject "^3.0.0"
     static-extend "^0.1.1"
 
-clean-css@^4.1.9:
-  version "4.2.3"
-  resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-4.2.3.tgz#507b5de7d97b48ee53d84adb0160ff6216380f78"
-  integrity sha512-VcMWDN54ZN/DS+g58HYL5/n4Zrqe8vHJpGA8KdgUXFU4fuP/aHNw8eld9SyEIyabIMJX/0RaY/fplOo5hYLSFA==
+clean-css@^5.1.1:
+  version "5.1.1"
+  resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-5.1.1.tgz#e0d168b5f5497a85f58606f009c81fdf89d84e65"
+  integrity sha512-GQ6HdEyJN0543mRTA/TkZ7RPoMXGWKq1shs9H86F2kLuixR0RI+xd4JfhJxWUW08FGKQXTKAKpVjKQXu5zkFNA==
   dependencies:
     source-map "~0.6.0"